Since marrying Prince William in 2011, Kate Middleton has been known by her royal title as Her Royal Highness The Duchess of Cambridge. But Kate's title will likely undergo a major change when Prince William succeeds the throne. Express.co.uk looks at how Kate and Camilla, Duchess of Cornwall's royal titles will differ in the future.

       Prince William is expected to be King one day when he succeeds his father, Prince Charles.

       And in the future, Kate is expected to be Queen, but not in the same sense as the current Queen Elizabeth II.

       Kate will not be Queen in her own right, as she will be a Queen Consort as the spouse of the King.

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       Queen Elizabeth II was born into the line of succession, whereas Kate joined the Royal Family through marriage.

       Only women born into the Royal Family and the line of succession can be a Queen in their own right.

       When Prince William succeeds the throne, Kate is likely to be known as Queen Consort.

       She will likely be titled as Queen Catherine with the style of Her Majesty rather than Her Royal Highness.

       While Kate is expected to be known as Queen one day, it is thought Camilla will have a different title.

       When Prince Charles is King, it would stand to reason that Camilla will be Queen Consort as Charles' wife.

       However, it was announced by Clarence House before Charles and Camilla married in 2005 that Camilla will use the title of 'Princess Consort' instead of being known as Queen.

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       The use of the 'Princess Consort' title for the spouse of the British monarch is unprecedented, but the title is used in other countries like Monaco that have a Sovereign Prince instead of a King.

       The decision for Camilla to be known as 'Princess Consort' may have been made out of respect for Charles' late ex-wife, Princess Diana, and the fact some people did not approve of Charles and Camilla's relationship at the time.

       Camilla's current royal title, Her Royal Highness The Duchess of Cornwall, is also unique for the spouse of the heir to the throne.

       Camilla does not use the Princess of Wales title despite being married to the Prince of Wales, and she is instead known publicly by the equivalent of Charles' Duke of Cornwall title.

       Since joining the Royal Family in 2005, Camilla's popularity with the British public has grown significantly, so she may be Queen Consort in the future if there is a change of heart.

       In 2010, journalist Brian Williams asked Prince Charles if Camilla would become "Queen of England, if and when you become the monarch.”

       In response, Prince Charles said: “That’s, well … We’ll see won’t we? That could be.”

       But Clarence House rebuffed the notion Camilla will be Queen back in 2020, stating the intention remained for Camilla to be known as Princess Consort in the future.